Refrigeration control system



J 1941- A. B NEWTON 2, 2

REFRIGERATION CONTROL SYSTEM Filed Oct. 27, 1959 a Bunnie: I

Alwin 3. Newton Patented Jan. 21, i941 ATENT OFFICE.

REFRIGERATION CONTROL SYSTEM Alwin B. Newton, Minneapolis Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application October 27, 1939, Serial No. 301,606

22 Claims.

This invention relates to a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space or compartment and a compressor for circulating refrigerant through the evaporators.

The prime object of this invention is to control the flow of refrigerant through the evaporators inlsuch a manner as to maintain desired temperature or other conditions in the space and to defrost intermittently the evaporators. In

carrying out this object of the invention, a valve is located between each evaporator and the suction side of the compressor for establishing or interrupting communication therebetween. Each valve is controlled by the frost condition of its associated evaporator, such as by the tempera- V ture of or the pressurewithin the evaporator, and by a thermostat responsive to-the temperature in the space or compartment. When the valves are closed the pressure in the evaporators increases to allow defrosting of the evaporators. When the thermostat calls for cooling the valves are opened providing their associated evaporators have defrosted and are closed when the therg5 mostat is satisfied. Thus, desired temperature conditions are maintained in the space or compartment and the evaporators are individually and intermittently defrosted.

Another object of this invention is to operate 39 sequentially the valves by the space or comparte ment thermostat so that when the temperature is low all of the valves are closed and as the temperature increases first one valve is opened and then another as the temperature increases further.

A further object of this invention is to provide air circulating means for circulating air over the evaporators and to operate the air circulating means at high speed when the evaporators m are performing a cooling function and to operate the air circulating means at slow speed when the evaporators are defrosting.

Another object of this invention is to cause operation 6f the compressor when any of the valves 4."; .are open to cause their associated evaporators m pressor when the suction pressure decreases to a predetermined low value. v

A further object of this invention is to prevent opening of the valves and starting of the compressor unless the head pressure is below a pre- 55 determined low value and to close the valves after they are once opened and stop the compressor after it has once started when the head pressure increases to a predetermined high value.

A still further object of this invention is to provide overload cut-out means in the high speed and low speed circuits of the compressor motor forclosing the valves and stopping the compressor when an overload condition occurs in either of these circuits.

Other objects and advantages will become ap-- parent to those skilled in the art upon reference to the specification, claims and drawing, in which is diagrammatically disclosed the preferred form of this invention.

The space or compartment to be conditioned or cooled is designated at I0. Cooling coils in .the form of evaporators II and i2 are utilized for cooling the space iii. A fan l3 operated by a two-speed motor i4 withdraws air from the space Ill through a duct l5, passes this air over the evaporator I I and discharges it in a cooled condition through a duct l6 into the space I 0. In a like manner, a fan- I! operated by a twospeed motor [8 withdraws air from the space M through a duct l9, passes this air over the evaporator l2 and discharges the cooled air through a duct into the space I0. While the evaporators ll and I2 have been shown exterior to the space Ill, these evaporators may be located within the space, l0.

Refrigerant is supplied to the evaporators Ii and I2 by a refrigerating apparatus generally designated at 22. The refrigerating apparatus may comprise a compressor 23 operated by a two-speed electric motor 2t. Compressed refrigerant passes from the compressor 23 through a high pressure line 25 into a condenser 26. Condensed refrigerant flows through a liquid line 21 from the condenser 26 and through branch liquid lines 28 and 29 to the evaporators and I2, respectively. Evaporated refrigerant is withdrawn from the evaporators H and I2 through branch suction lines 30 and 3| and through suction line 32 by the compressor 23. The flow of refrigerant into the evaporator II may be regulated by a thermostatic expansion valve 33 having a bulb 3Q responsive to the temperature of the refrigerant leaving the evaporator I I. In a like manner the flow of refrigerant to the evaporator l2 may be controlledby a thermostatic expansion valve 35 having a bulb 36 responsive,

tration, any number. may be utilized within the contemplation of this invention. A solenoid valve 31 is located in the branch suction line 38 and when this solenoid valve 31 is deenergized communication between the evaporator II and the suction side of the compressor 23 is interrupted. When the solenoid valve 31 is energized the evaporator II is placed in communication with the suction side of the compressor. A solenoid valve 38 is also located in the branch suction line 3| to interrupt communication between the evaporator l2 and the suction side of the compressor 23 when it is deeper-- gized and to cause communication between the evaporator I2 and the suction side of the compressor 23 when it is energized. When the valve 31 is closed the pressure within the evaporator H is allowed to build up to permit defrosting of the evaporator 38 is closed the pressure in the evaporator I2 is permitted to rise to defrost the evaporator l2.

Cooling water is supplied to the condenser 26 through a supply pipe 40 and is discharged from the condenser 26 through a discharge pipe 4|. A valve 42 controls the rate of flow of cooling water to the condenser 26 and this valve is con nected by a pipe 43 to the high pressure line 25 so that this valve is operated in accordance with changes in pressure in the condenser 26. Upon an increase in condenser pressure the valve 42 is graduatingly movedtowards an open position to increase the supply of cooling water to the condenser and ,upon a decrease in pressure the valve 42 is graduating moved towards a closed position to throttle the supply of cooling water to the condenser 28. For purposes of illustration it is assumed that the valve 42 is so arranged that it maintains the pressure in the condenser 26 between 135 pounds and 140 pounds.

The two-speed motor 24 which operates the compressor 23 may be controlled by a two-speed starter generally designated at 45. The starter 45 is in turn controlled by two relays 46 and 41, the arrangement being such that when either relay 46 or 41 is energized the starter 45 is controlled to operate the compressor at low speed and when both of the relays 46 and 41 are energized the starter 45 is controlled to .operate the compressor 23 at high speed. The relay 48 is controlled by a combined suction pressure and head pressure responsive controller 48 and the relay 41 is controlled by a combined suction pre sure and head pressure responsive controller 48. A two-stage thermostat 50 responsive to the temperature within the space or compartment l8 also controls the operation of the suction pressure and head pressure responsive controllers 48 and 49. The suction pressure and head pressure responsive controller 48 also controls the solenoid valve 31 and a relay 5| which contro sthe operation of the two-speed fan motor l4. Likewise the suction pressure and head pressure responsive controller 48 also controls the solenoid valve 38 :and controls a relay 52 which in turn controls the operation of the two-speed fan motor l8.

The suction pressure and head pressure responsive controller 48 may be of the type shown and described in application Serial No. 196,447, filed March 1'7, 1938. by Albert L. Judson and Carl G. Kronmiller. For purposes of illustration in this application this controller is shown to comprise a bellows 58 connected by a pipe 68 to the branch suction line 38 between the solenoid valve 31 and the evaporator Accordingly the bellows 58 is operated in response to the pressure existing With- Similarly, when the valve in the evaporator The bellows 58 operates a lever 8| pivotedon a fulcrum member 62 against the action of an adjustable tension spring 83. By suitably adjusting the tension in the spring 83 the pressure setting of this portion of the controller may be varied at will. The lever 8| operates contacts 64 and 65 and while these contacts 84 and 65 are electrically coupled together they are insulated from the lever 6|. The contact 64 is adapted to engage and disengage a contact member 36 carried by a terminal 61 and the contact 65 is adapted to engage and disengage a contact member 68 carried by a terminal 69. The contact members 88 and 68 are urged into engagement with concentrically located independently adjustable cams I8 and H. By independently rotating the cams I8 and H the contact members 68 and 68 may be independently positioned with respect to the contacts 64 and 65.

For purposes of illustration it is assumed that when the pressure within the evaporator-ll rises to 15 lbs. the contact 84 engages the contact 68 and when the pressure rises to 35 lbs. thecontact 35 engages the contact member 68. Upon a decrease in pressure in the evaporator II the contact 85 first disengages the contact member 88 at 35 lbs. and then the contact member 84 disengages the contact member 68 at 15 lbs. It is here assumed that the pressure in the evaporator H may rise to 35 lbs. only after the evaporator H has defrosted. v

The suction'pressure and head pressure responsive controller 48 may also comprise a bellows 13 connected by a pipe 14 to the liquid line 21 so that the bellows 13 is responsive to the pressure on the high pressure side of the refrigerating apparatus. The bellows1-3 operates a lever 15 fulcrumed on a fulcrum member 16 against the action of an adjustable tension spring 11. By suitably adjusting the tension spring 11 the pressure setting of this portion of the controller may be. adjusted at will. The lever 15 adjustably carries an abutment member 18 preferably made of insulating material. The abutment member 18 is provided with two abutment surfaces 18 and 80. The abutment surface 18 is adapted to engage a contact member 8 I carried by a terminal 82 to move the contact member 8| out of engagement with a contact 83. The abutment surface is adapted to engage a contact member 84 carried by the terminal 88 for moving the contact member 84 out of engagement with a contact 85. For purposes of illustration it is assumed that as the pressure on the high pressure side of the refrigerating apparatus rises to 140 lbs. the contact member 84 is moved out of engagement with the contact and when the pressure rises to 180 lbs. the contact member 8| is moved out of engagement with the contact 83. Upon a decrease in head pressure the contact member 8| first engages the contact 83 at 1 80 lbs.'and then the contact member 84 engages the contact 85 at lbs.

The suction pressure and head pressure responsive controller 48 also includes a relay having an operating coil 81 for operating bridge members 88 and 88. When the operating coil 81 is energized the bridge member 88 is moved into en- I gagement with contacts 88 and 8| and the bridge member 88 is moved into engagement with contacts 82 and 83. When the operating coil 81 is deenergized the bridge members 88 and 88 are moved out of engagement with their respective contacts by means of springs, gravity or other means, not shown. The controller 48 is also provided with a terminal 94 to facilitate external connections.

The suction pressure and head pressure responsive controller 49 which responds to the pressure in the evaporator i2 and to the pressure in the liquid line 21 is exactly the same as the suction pressure and head pressure .responsive controller 68 and therefore like reference charactors primed have been utilized to designate like parts. A further description of the construction of the controller 419 is therefore not considered necessary. a

The two-stage thermostat 50 may comprise a bellows 96 charged with a volatile fluid for operating a lever 97 against the action of an adjustable tension spring 98. The lever 97 operates a mercury switch 99 having electrodes H30, it! and W2. For purposes of illustration it is assumed that when the temperature within the compartment or space ill rises to 40 the mercury switch 99 is tilted to cause bridging of the electrodes 5% and i ill and when the temperature rises to 42 the mercury switch 99 is tilted to cause bridging of the electrodes H10, Hit and 402. When the temperature within the compartment or space "it decreases to 40 the switch 99 is tilted to bridge only the electrodes I and lo! and when the temperature decreases to 38 none of the electrodes m0, ill-l or B2 are bridged.

The relay 51! which controls the operation of the two-speed fan motor M may comprise an operating coll it l for operating a switch arm 195 with respect to contacts H16 and N37. The parts are so arranged that when the operating coil tilt is energized the switch arm W is moved into engagement with the contact Hi7 and when the operating coil i6 5 is deenergized the switch arm N35 is moved into engagement with the contact m6 by means of springs, gravity or other Accordingly a further description of the relay 52 is not considered necessary.

The two-speed starter 15 for the two-speed compressor motor 25 may comprise an'o-perating coil lid for operating a switch arm H-i with respect to a con-tact H2. When the operating coil H0 is energized the switch arm MI is moved into engagement with the contact H2 and when the operating coil Hill is deenergized the switch arm Hi is moved out of engagement with the contact i i2 by means of springs, gravity or other means, not shown. The switch arm Hi and the contact H2 control the starting and stopping of the compressor motor 2 3. The two-speed starter contact I 56 by means of springs, gravity or other means, not shown, to operate thecompressor motor 24 at low speed providing the switch arm HI is engaging the contact H2. A heater element ill located in the low speed circuit of the compressor motor 24 operates upon an overload condition in this circuit to flex a bimetallic element H8 carried by a terminal M9 for moving the bimetallic element H8 out of engagement with a contact lid. The heater iii, bimetallic element i it and contact I therefore form an overload cut-out arrangement responsive to overload conditions in the low speed circuit of the compressor motor 26. the high speed circuit of the compressor motor operates to heat a bimetallic element I22 carried by a terminal E23 for flexing the bimetallic element Q22 out of engagement with a contact i2i upon the occurrence of an overload condition in the high speed circuit of the compressor motor 2d. The heater Hi, the bimetallic element l2! and the contact 526! therefore form an overload cut-out responsive to overload conditions in the high speed circuit of the compressor motor 2d.

A heater iii located in have been utilized for designating like parts There is only one d ifierence between the relay 7 and the relay iii and that is that the switch arms Hi and iiiZofi the relay t? are electrically connected together by a conductor 835 while the corresponding switch arms of the relay 546 are not electrically connected together.

Power is supplied to the various control devices, relays, valves, fan motors and compressor motor by means of line wires H39 and M0 leading from some source of power, not shown.

With the parts in the position shown in the drawingeverything is shutdown. Assume now that the temperature within the space "or compartment it rises to 40 to bridge the electrodes H00 and HH, that the pressure in the evaporator H rises to 35 lbs. following defrosting of the evaporator H to move the contacts M and 65 into engagement with the contact members 66 and t8 and that the pressure in the pond-enser 25 is below 140 lbs. to cause the contact members 3i and 84 to engage the contacts 83 and 85. Under these conditions a starting circuit is completed from the line wire 139 through wires MI and M52, electrodes i083 and Hit of the mercury switch it, wire iii, contact 83, contact memher 8!, terminal 82, conductor M4, terminal 61, contact member 66, contacts 84 and 65, contact members 6'3 and 84, contact 85, conductor M5, contact 9!, conductor M6, operating coil 81, conductor it], terminal 94, wires its and M9, terminal H9, bimetallic element H8, contact 220, conductor iii), contact I24, bimetallic element 622, terminal I2 3and wire 15! back to the other line wine M0. Completion of this starting circuit energizes the operating coil Bl to move the bridge members 88 and 89 into engagement with their respective contacts.

Movement of the bridge member 88 into'engag-ement with its contacts fi and 9! completes a maintaining circuit which may be traced from .the line wire I39 through wires Hi! and M2, el'ec-' trodes H19 and idl of the mercury switch 99, wire I 13, contact 83, contact member 8!, terminal 32, conductor hi t, terminal 61, contact member 65, contact 64, conductor i52, contact 9%), bridge member 88, contact 9!, conductor M6, operating coil 81, conductor I41, terminal 94, wires I48 and I49, terminal II9, bimetallic element H8, contact I20, conductor I50, contact I24, bimetallic element I22, terminal I23 and wire I5I back to the other line wire I40. Completion of this circuit maintains the operating coil 81 energized until either the temperature within the space or compartment 10 decreases to 38 or until the pressure within the evaporator II decreases to 15 lbs. or until the pressure on the high pressure side of the refrigerating apparatus increases to 180 lbs. Upon the occurrence of any of these conditions the operating coil 81 is deenergized and cannot again be reenerg-ized until the above mentioned starting circuit is completed. As pointed out above, this starting circuit can be completed only when the temperature within the compartment or space I0 rises to 40, the pressure in the evaporator II rises to 35 lbs, and the pressure on the high pressure side of the refrigerating apparatus decreases to 140 lbs. It is here noted that the overload cut-outs in the two-speed starter 45 are both included in the starting and maintaining circuits outlined above so that if an overload condition should occur in either the low speed circuit orthe high speed circuit of the compressor motor 24 the open-at ing coil 81 will be deenergize'd.

Summing up, the operating coil 81 of the controller 48 may be energized only when the temperature in the space I0 rises to 38, theipressure inthe evaporator I I rises to 35 lbs., and the pressure on the high pressure side decreases to 140 lbs. and after the operating coil 81 has thus been energized it will remain energized until either the temperature within the space I0 decreasesto 38 or the pressure in the evaporator I I decreases to 15 lbs. or the pressure on the high pressure side of the refrigerating apparatus increases to 180 lbs. If an overload condition oc ours in either the slow speed or high speed circuits of the compressor motor 24 the operating coil 81 of the controller 48 is deenergized.

Assume now that the temperature within the space or compartment I0 rises to 42 to cause bridging of electrodes I00, I05 and I 02, that the pressure in the evaporator I2 rises to 35 lbs. to cause the contact 64' and 65' to engage the contact members 66 and 68' and that the pressure on the high pressure side of the refrigerating apparatus is below 140 lbs., to cause the contact members 8| and 84' to engage the contacts 83' and Under these conditions a starting circuit for the operating coil 81' of the controller 49 is completed and this starting circuit may be traced from the line wire I39 through wires MI and I42, electrodes I00 and I02 of the mercury switch 99, wire I53, contact 83', contact member 8|, terminal 82', conductor I54, terminal 61', contact member 66, contacts 64' and 65', contact members 68' and 84', contact 85, conductor I55, contact 9I', conductor I56, operating coil 81', conductor I51, terminal 94', wires I58 and I49, terminal H9, bimetallic element II8, contact I20, conductor I50, contact I24, bimetallic element I22, terminal I23 and wire I5I back to the other line wire I40. Completion of this starting circuit energizes the operating coil 81' of the controller 49 to move the bridge member 88' and 89' into engagement with their respective contacts.

Movement of the bridge member 88 into engagement with its contacts 90' and 9| completes a maintaining circuit which may be traced from the line wire I39 through Wires I4! and I42, electrodes I00 and I02 of the mercury switch 99, wire I53, contact 83', contact member 8|, terminal 02', conductor I54, terminal 61', contact member 66', contact 64', conductor I59, contact 90', bridge member 88', contact 9|, conductor I45; operating coil 81, conductor I51, terminal 94', wires I58 and I49, terminal II9, bimetallic element II8, contact I20, conductor I50, contact I24, bimetallic element I 22, terminal I23 and wire I5I back to the other line wire I40. Completion of this circuit maintains the operating coil 81 energized until either the temperature within the space or compartment I0 decreases to 40 or the pressure in the evaporator I2 decreases to 15 lbs. or the pressure on the high pressure side of the refrigerating apparatus increases to 180 lbs.

Summing up, the operating coil 81 of the controller 49 is energized only when the temperature within the compartment I0 rises to 42, the pressure in the evaporator I2 rises to 35 lbs. and the head pressure decreases to lbs. and after the operating coil 81' is once energized it is maintained energized until either the temperature within the compartment or space I0 decreases to 40 or the pressure in the evaporator I2 decreases to 15 lbs. or until the head pressure increases to lbs. It is here noted that the two overload cut-outs in the two-speed starter 45 are also connected in both the startingand maintaining circuits of the controller 49 so that upon the occurrence of an overload condition in either the low speed or high speed circuits of the compressor-motor 24 the operating coil 21 of the controller 49 is deenergized. I

When the operating coil 81 of the controller 48 is energized in the manner pointed out above to move the bridge member 89 into engagement with the contacts 92 and 93, a circuit is completed from the line wire I39 through wire I65, contact 92, bridge member 89, contact 93, wires I66, I61 and I68, solenoid valve 31, and wires I69, I10 and HI back to the other line wire I 40. Completion of this circuit energizes the solenoid valve 31 to establish communication between the evaporator II and the suction side of the compressor 23. When the operating coil 81 is deenergized this circuit is interrupted to close the solenoid valve 31 to interrupt communication between the evaporator II and the suction side of the compressor 23. Thus whenever the temperature within the space I0 rises to 38 and the evaporator II has defrosted to allow the pressure therein to rise to 35 lbs. and the head pressure has decreased to 140 lbs. the solenoid valve 31 is opened to cause the evaporator II to perform a cooling function. When either the temperature within the space I0 decreases to 38, or the pressure in the evaporator II decreases to 15v lbs., or the. head pressure increases to 180 lbs,

the solenoid valve 31 is closed to interrupt communication between the evaporator II and the suction side of the compressor 23. Thus the evaporator II no longer performs a cooling function and is allowed to defrost. After the .evaporator II has defrosted the valve 31 is again opened to cause the evaporator II to perform a cooling function providing the-thermostat 50 is demanding cooling and the pressure on the high pressure side of the refrigerating apparatus has decreased to 140 lbs.

When the operating coil 81 of the controller 48 is energized to cause the bridge member 89 to engage the contacts 92 and 93 a circuit is com pleted from the line wire I89 through wire I65, contact I92, bridge member 89, contact 93, wires I66 I61 and I13, operating coil I04 of the relay 5I and wires I14 I10 and I" back to the other line wire I40. Completion of this circuit energizes the operating coil I04 of the relay 5I to move the switch arm I05 into engagement with the contact I01. When this occurs a high speed circuit for the fan motor I4 is completed and this circuit may be traced from the line wire I39, through Wires MI and I16, switch arm I05, contact I01, wire I11, fan motor I4 and wires I18, I19 and HI back to the other line wire I40. Thus the fan I3 is operated at high speed whenever the operating coil 81 of the controller 48 is energized. When the operating coil 81 is deenergized the circuit through the operating coil I04 of the relay 5I is broken to cause the switch arm I05 to engage the contact I08 to complete a low speed circuit through the fan motor I4 which may be traced from the line wire I39 through wires MI and I16, switch arm I05, contact I08, wire I80, fan motor I4 and Wires I18, I19 and "I back to the other line wire I40. It will thus be seen that when the evaporator II is operating to cool the space I the fan I3 is operated at high Speed to circulate a maximum amount of cold air into the space I0. When, however, the operating coil 81 ofthe controller 48 is deenergized 'so that the valve 31 is closed to cause defrosting of the evaporator II the fan I3 is operated at low speed during this defrosting cycle. This will effectively prevent undue heating of the space I0 during the defrosting cycle. If desired the fan may be operated in an on and ofi manner instead of the two speed manner as ex-- plained.

When the operating coil 81 of the controller 49 is energized to move the bridge member 89' into engagement with the contacts 92' and 93' a circuit is completed from the line wire I39 through wire I82, contact 92, bridge member 89', contact 93, wires I83, I84 and I85, solenoid valve 38 and wires I86, I81 and "I back to the other line wire I40. Completion of this circuit energizes the solenoid valve 38 to establish communication between the evaporator I2 and the suction side of the compressor 23 whereupon the evaporator I2 performs a cooling function. When the operating coil 81 is deenergized this circuit is broken and the solenoid valve 38 is closed to interrupt communication between the evaporator I2 and the suction side of the compressor 23 whereupon the evaporator I2 is placed on the defrosting cycle. When the operating coil 81' is energized another circuit is completed from the line wire 39 through wire I82, contact 92, bridge member 89, contact 93, wires I83, I84 and I88. operating coil I04 of the relay 52 and wires I89, I81 and HI back to the other line wire I40. Completion of this circuit energizes the operating coil I04 to move the switch arm I into engagement with the contact I01 to complete a. high speed circuit for the fan motor I8 which may be traced from the line wire I39 through wires MI and I9I, switch arm I05, contact I01, wire I92, fan motor I8 and wires I93, I19 and Ill back to the other line wire I40. I'hus the fan I1 is operated at high speed while the evaporator I2 is performing a cooling function. When the operating coil 81' of the controller 49 is deenergized the circuit through the operating coil I04 of the relay 52 is broken whereupon the switch arm I05 engages the contact I06 to complete a slow speed circuit for the fan motor I8, which may be traced from the line wire I39 through wires MI and I9I,' switch arm I05, contact I06, wire I94, fan motor I8 and wires I93, I19 and HI back to the other line wire I40. Thus when the evapo-- rator I2 is on a defrosting cycle the fan I1 is operated at slow speed. It is therefore seen that the solenoid valve 38 and the fanmotor I8 are operated in exactly the same way as the solenoid valve 31 and the fan motor I4 are operated, the only distinction being that the solenoid valve 38 is opened and the fan I1 is placed on high speed operation when the temperature within the space I0 rises to 42 while the solenoid valve 31 is opened and the fan I3 is placed on high speed operation when the temperature within the space I0 rises to 40. Thus-a two-stage operation is obtained. If desired, the two valves 31 and 38 and the two fans I3 and I1 could be operated at the same temperature for single stage operation.

When the operating coil 81 of the controller 48 is energized still another circuit is completed from the line wire I39 through wire I65, contact 92, bridge member 89, contact 93, wires I66 and 200, operating coil I30 of the relay 48 and wire 20I back to the other line wire I40. Completion of this circuit energizes the operating coil I30 to move the switch arms I3I and I32 into engagement with contacts I33 and I34. 1 When the operating coil 81 of the controller 49 is energized a circuit is completed from the line wire I39 through wire I82, contact 92", bridge member 89', contact 93, wires I83 and 202, operating coil I30 and wire 203 back to the other line wire I40. Completion of this circuit energizes the operating coil I30 .015 the relay 41 to move the switch arms I3I and I32 into engagement with the contacts I33 and I34.

When the operating coil I30 is energized to move the switch arm I3I into engagement with the contact I33 a circuit is completed from the line wire I39, through wire 205, contact I33, switch arm I3I, wires 206 and 201, operating coil H0 and wires 208 and 209 back to the other line wire I40. Thus when the relay 46 is energized the operating coil IIO of the two-speed starter 45 is energized. When the operating coil I30 of the relay 41 is energized to move the switch arm I3I into engagement with the contact I33, a circuit is completed from the line wire I39 to wire IIO, contact I33, switch arm I3I, wires 2 and 201, operating coil H0 and wires 208 and 209 back to the other line wire I40. Thus when the relay 41 is energized a circuit is also completed through the operating coil IIO of the two-speed starter 45. In other words, the relays 46 and 41 are arranged in parallel for controlling the energization of the operating coil IIO of the twospeed stanter 45 so that when either of these relays is energized the operating coil I I0 of the twospeed starter 45 is energized. I

When the operating coil IIO of the two-speed starter 45 is energized to move the switch arm III into engagement with the contact II2 a. low speed circuit for the compressor motor 24 is completed and this circuit may be traced from the line wire I89 through wire 2I3, switch arm III, contact II2, wire 2I4, switch arm II4, contact IIG, wire 2I5, heater II1, wire 2I6, compressor motor 24 and wire 2 I1 back to the other line wire I40. Accordingly when either relay. 46 or 41 is energized the compressor motor 24 and hence the compressor 23 are operated at low speed.

When. both relays 46 and 41 are energized a circuit is completed from the line wire I39 through \mre 2I0, contact I33, switch arm I3I, conductor I35, switch arm I32, contact I34, wire 220, contact I34, switch arm I32, wire 22I, operating coil I I3, and wire 209 back to the other line wire I40. Completion of this circuit energizes the operating coil II3 of the two-speed starter 45 to move the switch arm I I4 into engagement with the contact H to complete a high speed circuit for the compressor motor 24. This high speed circuit may be traced from the line wire I39 through wire 2I3. switch arm III, contact II2, wire 2I4, switch arm II4, contact H5, wire 223, heater I2I, wire 224, compressor motor 24, and wire 2I1 back to the other line wire I40. Accordingly when both relays 46 and 41 are energized the compressor motor 24 is operated at high speed.

The operation of the complete system may be summarized briefly as follows:

When the space temperature decreases to 38, the compressor 23 is stopped, the solenoid valves 31 and 38 are closed to allow the'evaporators II and I2 to defrost and the fans I3 and I1 are operating at low speed to assist the defrosting of the evaporators.

When the space temperature increases to 40 and providing the evaporator II has defrosted and the head pressure is below 140 lbs. the solenoid valve 31 is opened to cause the evaporator I I to perform a cooling function, the fan I3 is operated at high speed, and. the compressor 23' is operated at low speed. The solenoid valve 31 then remains open, the fan I3 remains operating at high speed and the compressor 23 remains operating at low speed until either the temperature in the space I 0 decreases to 38 or the pressure in the evaporator II decreases to 15 lbs. or the head pressure increases to 180 lbs.

If while the evaporator I I is performing a cooling function as outlined immediately above the load should increase to cause the space temperture to rise to 42 and providing the evaporator I2 has defrosted and the head pressure is below 140 lbs., then the solenoid valve 38 is opened to cause the evaporator I2 to perform a cooling function. At the same time the fan I1 is operated at high speed and the compressor 23 is operated at high speed. Under these conditions the system operates to afford maximum.

cooling, both of the evaporators II and I2 performing their cooling functions at this time. The evaporator I2 will continue to perform its cooling function until either the temperature within the space I0 decreases to 40 or the pressure in the evaporator I2 decreases to 15 lbs. or the head pressure increases to 180 lbs. ,If any of these contingencies occur then the solenoid valve 38 is closed, the fan I1 is operated at low speed and the compressor 23 is operated at low speed.

Assume now that the system is shut down as illustrated in the drawing and that the temperature within the space I 0 rises to 40. Also assume that the evaporator II has not defrosted and therefore it is impossible to open the solenoid valve 31. Since the evaporator I2 was placed on the defrosting cycle before the evaporator II was placed on the defrosting cycle the evaporator I2 will become defrosted before the evaporator I I. Since the evaporator II cannot be placed in operation the temperature in the space I 0 continues to rise and when it rises to 42 the solenoid valve 38 will open to cause the evaporator I2 to perform a cooling function since at this time the evaporator I2 is defrosted. The compressor 23 is then operated at low speed and the fan I1 is operated at high speed. As soon as the evaporator II is defrosted the solenoid valve 31 will be opened to place the evaporator II in operation, the fan I3 will be operated at high speed and the compressor 23 will be operated at high speed. The system will then continue to operate in the normal manner until the temperature Within the space I0 decreases to 38.

Since the solenoid valves 31 and 38 cannot be opened and since the compressor '23 cannot be placed in operation unless the head pressure is below 140 lbs. the system is protected against damage due to the failure of supply of condenser water. Also upon the occurrence of an overload condition in either the low speed or high speed clcuits of the compressor motor the compressor is shut down. .Since both solenoid valves 31 and 38 are controlled by a single twostage thermostat 50 the proper sequence of operation may at all times be assured and the control point of the thermostat may be easily raised or lowered without upsetting this sequence of operation.

If the head pressure cut-out setting of the controller 48 is set at, say, 180 lbs. and the head pressure cut-out setting of the controller 49 is set at, say, 185 lbs., then upon an increase in head pressure to 180 lbs. only the relay 46 drops out, the other relay 41 remaining energized. Thus, the compressor is placed on low speed operation but if the head pressure increases to 185 lbs. then the relay 41 also drops out to stop the compressor. Accordingly, if .there should be only a partial failure in the supply of condensing water, the compressor may be placed on low speed operation and still some cooling may be accomplished.

Although for purposes of illustration one form of this invention has been disclosed, other forms thereof may become apparent to those skillled in the art upon reference to this disclosure and therefore this invention is to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling 2. space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator for controlling the flow of refrigerant therethrough, control means responsive to the temperature of the space for opening the valves upon a call for cooling to render their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the condition thereof for preventing opening of the valve of that evaporator until that evaporator has defrosted.

2. In a control system for a refrigerating apparatus having a pluralityoi evaporators for cooling 9. space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting communication therebetween, control means responsive to the temperature of the space for opening the valves upon a call for cooling to render their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the condition thereof for preventing opening of the valve of that evaporator until that evaporator has defrosted.

3. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting communication therebetween, control means responsive to the temperature of the space for opening the valves upon a call for cooling to render their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the pressure therein for preventing opening of the valve of that evaporator until the pressure therein has risen to a defrosting value.

4. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator for controlling the flow of refrigerant therethrough, air circulating means associated with each evaporator for circulating air thereover, control means responsive to the temperature of the space for opening the valves and for controlling the air circulating means to increase the circulation of air over the evaporators upon a call for cooling to render their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the condition" thereof for preventing opening the valve of that evaporator and increasing the circulation of air thereover until that evaporator has defrosted.

5. In a control system for a refrigerating apparatus having a plurality of eraporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, thecornbination of, a valve associated with each evaporator for controlling the flow of refrigerant therethrough, air circulating means associated with each evaporator for circulating air thereover and operated at low speed or high speed, control means responsive to the temperature of the space for opening the valves and. for operating the air circulating means at high speed upon a call for cooling to render their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the condition thereof forpreventing opening of the valve and high speed operation of the air circulating means of ,that evaporator until that evaporator has defrosted.

' 6. In a control system for a refrigerating ap- I paratus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporaand for increasing the speed of operation of the compressor as more valves are opened.

. 7. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporaincrease the circulation of air over the evaporators upon a call for cooling to render their associated evaporators effective for performing a cooling function, control means associated with each evaporator and responsive to the condition thereof for preventing opening the valve of that evaporator and increasing the circulation of air thereover until that evaporator has defrosted, and means for operating the compressor at" low speed when one of the valves is opened and for increasing the speed of operation of the compressor as more valves are opened:

8. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator for controlling the flow of re frigeranttherethrough, control means responsive to the temperature of the space for progressively opening the valves as the space temperature increases to render sequentially their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the condition thereof for preventing opening of the valve of that evaporator until that evaporator has defrosted.

9. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor I for establishing and interrupting communication ,therebetween, control means responsive to the temperature of the space for progressively opening the valves as the space temperature increases to render sequentially their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the condition thereof for preventing opening of the valve of that evaporator until that evaporator has defrosted.

10. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting communication therebetween, control means responsive to the temperature of the space for progressively opening the valves as the space temperature increases to render sequentially their associated evaporators effective for performing a cooling function,

and control means associated with each evapo- F paratus having a plurality of evaporators for cooling a space, a condenser and acompressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator for controlling the flow of refrigerant therethrough, control means responsive to the temperature of the space for progressively opening the valves as the space temperature increases to render sequentially their associated evaporators effective for performing a cooling function, control means associated with each evaporator and responsive to the condition thereof for preventing opening of the valve of that evaporator until that evaporator has defrosted, and means for operating the compressor at low speed when one of the valves is'opened and for increasing the speed of operation of the compressor as more valves are opened.

12. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a; condenser and a compressor for circulating refrigerant throughvthe evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting com-,

munication therebetween, control means responsiveto the temperature of the space-for opening the valves upon a call for cooling to render their associated evaporators effective for performing a cooling function, and control means associated with each evaporator and responsive to the pressure therein for preventing opening of the valve of that evaporator until the pressure therein has risen to a defrosting value and for closing the valve of that evaporator when the pressure therein decreases to a predetermined low value.

13. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a. space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting communication therebetween, control means responsive to the temperature of the space for opening the valves upon a call for cooling to ten. der their associated evaporators efiective for performing a cooling function, control means associated with each evaporator and responsive to the pressure therein for preventing opening of the valve of that evaporator until the pressure therein has risen to a defrosting value, means for operating the compressor at low speed when one of the valves are opened and for increasing the speed of operation of the compressor as more valves are opened, and means for closing the valves and stopping operation of the compressor when the pressure on the low pressure side of the refrigerating apparatus decreases to a predetermined low value. I

14. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evap forming a cooling function, control means associated with each evaporator and responsive to the pressure therein for preventing opening of the valve of that evaporator until the pressure therein has risen to a defrosting value, means for operating the compressor at low speed when one of the valves is opened and for increas-- ing the speed of operation of the compressor as more valves are opened, and means for closing the valves and stopping operation of the compressor when the pressure on the low pressure side of the refrigerating apparatus decreases to a predetermined low value.

15. In a control system for a refrigerating 'apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting communication therebetween, control means responside of the refrigerating apparatus for preventthe valves upon a call for cooling to render their associated evaporators effective for performing a cooling function, control means associated with each evaporator and responsive to the pressure therein for preventing opening of the valve of that evaporator until the pressure therein has risen to a defrosting value, and means responsive to the pressure on the high pressure side of the refrigerating apparatus for preventing opening of the valves until the pressure decreases to a predetermined low value.

16. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators, the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting communication therebetween, control means responsive to the temperature of the space for opening the valves upon a. call for cooling to render their associated evapora-tors effective for performing a cooling function, control means associated with each evaporator and responsive to the pressure therein for preventing opening of the valve of that evaporator until the pressure therein has risen to a defrosting value, and means responsive to. the pressure on the high pressure side of the refrigerating apparatus for preventing opening of the valves until the pressure decreases to a predetermined low value and for closing the valves when the pressure increases to a predetermined high value.

1'7. In control system for a. refrigerating apparatus having a plurality of evaporators for cooling a space, a condenser and a compressor for circulating refrigerant through the evaporators,

the combination of, a valve associated with each evaporator and located between the evaporator and the low pressure side of the compressor for establishing and interrupting communication therebetween, control means responsive to the temperature of the space for opening the valves upon a call for cooling to render their associated evaporators effective for performing a cooling function, control means associated with each evaporator and responsive to the pressure therein for preventing opening of the valve of that evaporator until the pressure therein has risen to a. defrosting value, means for operating the compressor at low speed when one of the valves is opened and for increasing the speed of operation of the compressor as more valves are opened, and means responsive to the pressure on the high pressure side of the refrigerating apparatus for preventing opening of the valves and for preventing starting of the compressor until the pressure decreases to a predetermined low value.

18. In a control system for a refrigerating apparatus having evaporator means, a compressor for circulating refrigerant through the evaporator means and a, multispeed motor for operating the compressor, the combination of, means for completing a low speed circuit to the compressor motor for operating the compressor at low speed, means for completing a high speed circuit to the compressor motor for operating the compressor at high speed, means including overload cutout means responsive to the current flow in the low speed circuit and the high speed circuit for stopping the compressor motor when an overload condition occurs in either circuit, and means for preventing restarting of the compressor motor until the pressure on the low pressure side of the refrigerating apparatus increases to a predetermined high value.

19. In a control system for a refrigerating apparatus having evaporator means, a compressor for circulating refrigerant through the evap orator means and a multispeed motor for operating the compressor, the combination of, means for completing a low speed circuit to the'compressor motor for operating the compressor at low speed, means for completing a high speed circuit to the compressor motor for operating the compressor at high speed, means including overload cut-out means responsive to the current flow in the low speed circuit and the high speed circircuit for stopping the compressor motor when an overload condition occurs in either circuit, and means for preventing restarting of the compressor motor until the pressure on the high pressure side of the refrigerating apparatus decreases to a predetermined low value.

20. In a control system for a refrigerating apparatus having a plurality of evaporators and a multispeed motor driven compressor for the evaporators, a valve associated with each evaporator for controlling the flow of refrigerant therethrough, control means responsive to the demands on the refrigerating system for opening said valves to render their associated evaporators effective, means for completing a low speed circuit to said compressor motor when only one of said valves is open, means for completing a higher speed circuit to said compressof motor when more than one of said valves is open, means including overload cut-out means responsive to the current flow in the low speed circuit and the higher speed circuit for stopping the compressor motor when an overload condition occurs in either circuit, and means for preventing opening of any valve until the suction pressure on its evaporator rises to a predetermined value whereby said compressor motor cannot be restarted after it is stopped by an overload condition until the low side pressure on at least one of said evaporators has risen to said predetermined value.

21. In a control system for a refrigerating apparatus having a plurality of evaporators and a multispeed motor driven compressor for the evaporators, a valve associated with each evaporator for controlling the flow of refrigerant there- 1 through, control means responsive to the demands on the refrigerating system for opening said valves to render their associated evaporators effective, means for completing a low speed circuit to said compressor motor when only one of said valves is open, means for completing a higher speed circuit to said compressor motor when more than one of said valves is open, means including overload cut-out means responsive to the current flow in the low speed circuit and the higher speed circuit for stopping the compressor motor when an overload condition occurs in either circuit, and means for preventing opening of any valve unless the head pressure of the refrigerating apparatus is below a predetermined value whereby said compressor motor cannot be restarted after it is stopped by an overload condition until the head pressure of the refrigerating apparatus has fallen to said predetermined value.

22. In a control system for a refrigerating apparatus having a plurality of evaporators for cooling a space and a multispeed motor driven compressor for the evaporators, a valve associated with each evaporator for controlling the flow of refrigerant therethrough, control means responsive to the temperature of a space for opening said valves to render their associated evaporators effective when the space temperature rises, means for completing a low speed circuit to said compressor motor when only one of said valves is open, means for completing a higher speed circuit to said compressor motor when more than one of said valves is open, means including overload cut-out means responsive to the current flow in the low speed circuit and the higher speed circuit for stopping the compressor motor when an overload condition occurs in either circuit, and means for preventing opening of any valve until the suction pressure on its evaporator rises to a predetermined value and the head pressure on the system falls to a predetermined value whereby said compressor motor cannot be restarted after it is stopped by an overload condition until the low side pressure on at least one of said evaporators has risen to said predetermined value and the head pressure on the system has lowered to its predetermined value.

ALWIN B. NEWTON.

I CERTIFICATE OF CORRECTION.

January' 21, 1911.1.

Patent No. 2,229,501.

- ALWIN B. NEWTON. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 8, secline 25., claim 15, strike out "'side of the refrigerating apps.-

ond column,

I and insert instead the syllable and words +sive to the ratus for prevent-" temperature of the space for opening"; and that the sa shou the record of the case in the Patent Office. A

Signed and sealed this 25th day of March, A. D. 19LL1.

Henr Van Arsda'le,

(Seal) Acting Commissioner of Pat ents.

id Letters Patent id be read with this correction therein that the same may confonn to. 

